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How does the Coombs test help detect blood incompatibility?

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blood disease Peripheral blood smear revealing histopathologic features indicative of a blast crisis in a case of chronic myelogenous leukemia (CML). Blast crisis occurs when one-fifth to one-third of the cells in the blood or bone marrow are immature blood cells, or blast cells. This phase of CML is characterized by fever, weakness, and an enlarged spleen.

The Coombs test, also known as the antiglobulin test, is a critical diagnostic tool used to detect blood incompatibility by identifying the presence of antibodies bound to red blood cells.12

When incomplete antibodies react with red cells, they coat the cell membrane with gamma globulin or complement, but this process does not cause visible clumping (agglutination) in a standard saline solution. The Coombs test utilizes Coombs serum—which contains antihuman globulin—to bridge these coated cells. When this serum is added to the washed red blood cells and centrifuged, it binds to the antibodies already present on the cells, causing them to agglutinate and become visible.1

This test is essential for:
* Transfusion Compatibility: It is used during cross-matching to detect antibodies in a recipient's serum that would otherwise cause life-threatening immune destruction of donor red blood cells.2
* Hemolytic Disease: It helps identify antibodies in cases of hemolytic disease of the newborn, where a mother may have developed antibodies against the blood type of her fetus.132
* Autoimmune Conditions: It detects autoantibodies in certain drug-induced or autoimmune hemolytic anemias.12